Stems long-creeping, 2--4 mm diam. Leaves monomorphic, dying back in winter, often 1--2 cm apart, ca. 25--75 cm. Petiole straw-colored, (7--)20--45 cm × 1.5--3 mm, at base with scales tan, lanceolate, glabrous or marginally hairy. Blade broadly deltate, about as broad as long, (8--)15--33 cm, proximal pinnae longest and narrowed at base, usually spreading or slightly ascending. Pinnae 7--20 × 2--6(--8) cm, all connected by wing along rachis, deeply pinnatifid; segments entire or largest pinnatifid about halfway to costule; proximal pair of veins from adjacent segments meeting margin above sinus, veins often forked. Indument abaxially of moderately to densely set hairs mostly 0.1--0.25 mm along costae and veins, also of yellowish stalked glands 0.1 mm on veins and blade tissue, costae with whitish to light tan, narrowly lanceolate, spreading, marginally hairy scales to ca. 1.5 mm. Sori subterminal on veins. 2 n = 60. In moist woods, usually in full shade, often in moderately acid soils; 0--1000 m; Ont., Que.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va., Wis. G. A. Mulligan and W. J. Cody (1979) reported hybrids between Phegopteris hexagonoptera and P. connectilis from a few localities in Quebec, New Brunswick, and Nova Scotia. These hybrids are apogamous and have a chromosome number of 2 n = 120.
Much like no. 1 [Thelypteris phegopteris (L.) Sloss]; rhizome sparingly hairy and densely scaly; lvs 3-8 dm; petiole hairy and sparsely scaly below, smooth above; blade to 4 dm, mostly a little wider than long, bipinnatifid, the lowest pair of pinnae the largest, widely spreading, the rachis winged throughout; pinnae to 7 cm wide; veins simple or rarely a few forked; scales of the rachis few, whitish, lance-triangular; 2n=60. Moist woods and thickets; Que. and Me. to Ont. and Minn., s. to n. Fla. and Tex. (Phegopteris h.; Dryopteris h.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.